Senior running back A.J. Blue walked into North Carolina’s locker room Saturday and saw something he hadn’t seen since Sept. 7 — his teammates’ smiling after a game.

After four straight losses that ended any championship hopes (and two bye weeks), the Tar Heels finally put together a dominant performance in a 34-10 win over Boston College at Kenan Stadium.

“That felt good — that’s the kind of feeling we want to have every game,” Blue said. “It was getting pretty ugly. Guys were starting to question themselves and question each other. But that’s what you do as a family — you come together and when you win, you celebrate together.”

There was plenty to smile about. Many of the mental mistakes were eliminated — UNC (2-5, 1-3 ACC) didn’t commit a turnover for the first time this season and had fewer penalties than Boston College (3-4, 1-3), the least-penalized team in the ACC.

On offense, the Tar Heels converted all five red zone opportunities into touchdowns as their two-quarterback rotation worked seamlessly, with Bryn Renner completing 18 of 21 passes for 227 yards and two scores while dual threat Marquise Williams ran for a team-high 55 yards and a score on seven carries.

On defense, UNC only allowed Boston College to get inside the 35 once until its final series and limited the Eagles to 59 passing yards — the fewest for an opponent since Clemson’s 37 in 1997 — as they held an ACC team to 10 points for the first time since the Butch Davis era.

Andre Williams, who entered fifth in the nation in rushing average (139.7), gained 172 yards on 26 carries for BC. But fourth-year quarterback Chase Rettig was just 10 of 20 for 57 yards and was sacked four times against what was statistically the ACC’s worst defense.

Senior defensive end Kareem Martin got to Rettig on third down on consecutive drives in the third quarter while the Tar Heels were still hanging on to a 20-7 lead. Martin had four tackles for loss last week against Miami, when the Tar Heels gave up a last-minute touchdown drive and lost 27-23.

“(Martin’s) been the most consistent guy for us all year, but in the last two games he’s really come on hard,” Fedora said. “He knows his career here is coming to an end and I think he sees that and he wants to get everything out of it”

The only turnover of the game occurred on the second play when the Eagles fumbled a handoff. Linebacker Jeff Schoettmer fell on it at the BC 35, and UNC took advantage when freshman Ryan Switzer scored his first career touchdown on a 13-yard catch.

The Tar Heels missed the extra point and Andre Williams responded with a 56-yard touchdown to put the Eagles ahead 7-6.

But after going three-and-out twice, Marquise Williams entered for the first time on UNC’s fourth possession and engineered a 15-play, 81-yard drive to put the Tar Heels in front for good.

“He brings athleticism to the table and he had some great runs out there today, and he can throw the ball as well,” Renner said. “For our offense to grow … he’s going to need to be a big factor.”

Renner, who completed his first 10 passes, then hit Bug Howard for a 10-yard touchdown with 52 seconds left in the second quarter to give the Tar Heels a 20-7 lead at halftime. It was the first of two touchdowns for Howard, who also caught a 17-yarder from Williams with 19 seconds left in the third quarter.

“This is what we expected each week,” Blue said. “We expected to eliminate the big plays, stop the penalties. We’ve been a very penalty-oriented team this year. I guess it was lack of focus, lack of preparation. Today guys were prepared, and everything we did today we finished.”

NOTES — Eric Ebron, one of the nation’s top tight ends, had his first two career carries for seven yards. The junior, who played a game on the defensive line against N.C. State last year, lined up in the backfield in a “turbo set” alongside Blue and running back T.J. Logan. … Tommy Hibbard’s 76-yard punt in the first quarter was the longest by a Tar Heel in 24 years and the sixth-longest in school history. … A bad snap on UNC’s first kick attempt broke a streak of 191 consecutive made extra points, the second-longest streak in the country behind Texas Tech (249). … With injuries to bandits Norkeithus Otis (limited) and Darius Lipford (out), freshman Mikey Bart made his first start. He recorded a sack on a fourth-and-1 in the fourth quarter. … Sophomore T.J. Thorpe, a Jordan High School graduate, had a career-long 33-yard catch.